Japanese Patent Application Laid-Open No. 2015-084637, Japanese Patent Application Laid-Open No. 2015-065731 and Japanese Patent Application Laid-Open No. 2015-076921 each disclose a direct power converter. This direct power converter includes a diode rectifier, an inverter, and a charge and discharge circuit.
The diode rectifier full-wave rectifies a single-phase AC voltage, and outputs a rectified voltage after rectification across a pair of DC power supply lines (a DC link).
The charge and discharge circuit is provided to the DC link, and includes a buffer circuit and a boost circuit. The buffer circuit has a switch and a capacitor connected in series to each other between the pair of DC power supply lines. When the switch is conducting, the capacitor discharges to provide power to the DC link.
The boost circuit boosts the rectified voltage from the diode rectifier to charge the capacitor. This allows the charge and discharge circuit to receive power from the DC link. An input voltage (a DC voltage from the DC link) of the inverter matches the boosted voltage for the capacitor when the above-mentioned switch is conducting, and matches the rectified voltage when the switch is not conducting. The inverter receives the DC voltage from the DC link as an input, converts it into an AC voltage, and outputs the AC voltage.